A nylon extraction system

Abstract

The nylon extraction system provided by the utility model comprises a pre-extraction tank, a water-material separation tank, an extraction tower, and a dehydration device which are arranged in sequence. The discharge pipeline of the pre-extraction tank is divided into at least two routes, one of which leads to the extraction tower, and the other skips the extraction tower and directly leads to the dehydration device. When the extraction tower works normally, the discharge pipeline of the pre-extraction tank is connected with the extraction tower to carry out the extraction process of slices; when the extraction tower fails, the discharge pipeline of the pre-extraction tank skips the extraction tower and directly connects with the next process. Since the slices have been preliminarily extracted in the pre-extraction tank, the next process is directly carried out in a short time without causing the accumulation of small molecular monomers. This arrangement ensures the continuous operation of the extraction system and avoids the losses caused by the shutdown of the production line.

Description

Technical Field

[0001] The utility model relates to a nylon production system, in particular to a nylon extraction system. Background Art

[0002] The production of conventional nylon relies heavily on petroleum resources. However, since petroleum is a non-renewable resource, dependence on petroleum is not conducive to the sustainable development of nylon and may also cause environmental problems during production and use. In order to solve this problem, bio-based nylon 56 (also known as bio-based PA56 or bio-based polyamide 56) came into being. This material is polypentamethylene adipate produced by the polymerization reaction of bio-based pentamethylenediamine and petroleum-based adipic acid.

[0003] During the initial development and commissioning of the drying and solid phase polymerization equipment for bio-based nylon 56, we noticed that the amount of monomer precipitation of bio-based nylon 56 chips produced by the polymerization process was significantly higher than that of nylon 66 chips when they were directly dried and solid phase thickening. These precipitated monomers tend to form crystals in the drying and solid phase thickening equipment, leading to blockage of pipes and equipment, thereby increasing system resistance. In addition, if these monomers are not effectively extracted, they may cause broken or floating yarns during the spinning stage, affecting the overall quality of the product. Especially in the solid phase polymerization process, due to the high process temperature, the amount of monomer precipitation of bio-based nylon 56 is 5 to 8 times that of nylon 66. Therefore, the extraction system is very important in the production of nylon.

[0004] Traditional nylon 66 extraction equipment is difficult to effectively extract these precipitated monomers. This situation not only poses a major challenge to the operation of continuous drying and solid phase viscosity increasing equipment, but also makes it difficult to effectively control and improve the quality of the final slices. In addition, the stable operation of the extraction equipment is also particularly important for the production of nylon. Once the extraction equipment fails, the entire production line will stop, seriously affecting production efficiency. Utility Model Content

[0005] In order to solve the above problems, the utility model provides a nylon extraction system, and the specific scheme is as follows:

[0006] A nylon extraction system, characterized in that the nylon extraction system comprises a pre-extraction tank, a water-material separation tank, an extraction tower, and a dehydration device which are arranged in sequence, and the discharge pipeline of the pre-extraction tank is divided into at least two routes, one of which leads to the extraction tower, and the other skips the extraction tower and directly leads to the dehydration device.

[0007] In the above, the discharge pipeline is divided into at least two routes. A three-way valve may be connected to the discharge pipeline of the extraction tank to divide the discharge pipeline into two routes, or two discharge ports may be provided at the bottom of the pre-extraction tank, leading to the extraction tower and the dehydration equipment after the extraction tower respectively.

[0008] Optionally, the dehydration equipment is one or more of gravity dehydration equipment, screening dehydration equipment, centrifugal dehydration equipment, and filtration dehydration equipment.

[0009] Optionally, the nylon extraction system is arranged between the polymerization section and the drying section.

[0010] Optionally, the nylon extraction system is provided with a water circulation system, and the water circulation system circulates the water separated by the dehydration equipment to the extraction tower.

[0011] Optionally, the circulating water pipeline passing through the water circulation system is divided into three routes, and the three pipelines are arranged from bottom to top at the interfaces on the extraction tower. The first route directly leads to the bottom of the extraction tower, the second route is provided with a heat exchanger and leads to the bottom of the extraction tower, and the third route is provided with a heat exchanger and leads to the middle of the extraction tower.

[0012] Optionally, an overflow port is provided on the extraction tower.

[0013] Optionally, a heating area is provided on the tower body of the extraction tower.

[0014] Beneficial effects:

[0015] The nylon extraction system provided by the utility model has a pre-extraction tank that can preheat and preliminarily extract the slices, so as to avoid the slices at room temperature from affecting the temperature in the extraction tower, ensure the stability of the temperature in the extraction tower, and thus improve the extraction efficiency of the extraction tower. The discharge pipeline of the pre-extraction tank is set to two routes, one leading to the extraction tower, and the other skipping the extraction tower and directly leading to the dehydration equipment. When the extraction tower works normally, the discharge pipeline of the pre-extraction tank is connected to the extraction tower to carry out the extraction process of the slices; when the extraction tower fails, the discharge pipeline of the pre-extraction tank skips the extraction tower and directly connects to the dehydration equipment. Since the slices have been preliminarily extracted by the pre-extraction tank, direct dehydration in a short time for the subsequent process will not cause the accumulation of small molecular monomers. After the extraction tower is repaired, the pre-extraction tank is connected to the extraction tower to continue the extraction process. This arrangement ensures the continuous operation of the extraction system and avoids the losses caused by the shutdown of the production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the overall schematic diagram of the nylon extraction system of the utility model

[0017] The following are the descriptions of the reference numerals:

[0018] 100. Polymerization section 200. Drying section 310. Pre-extraction tank 311. Rotary valve 312. Mud pump 313. First three-way reversing valve 314. Second three-way reversing valve 315. Bypass pipeline 320. Water-material separation tank 330. Extraction tower 331. First water inlet 332. Second water inlet 333. Third water inlet 334. Overflow port 340. Centrifugal dryer 350. Water circulation system 400. Fresh desalted water DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiment of the utility model clearer, the technical scheme in the embodiment of the utility model will be further clearly and completely described in the following text in combination with the drawings. Obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiments. For the sake of clarity and conciseness, not all the features of the actual implementation are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual embodiment in order to achieve the specific goals of the developers. In order to avoid obscuring the utility model due to unnecessary details, only the device structure closely related to the scheme according to the utility model is described in the drawings and descriptions. In order to more clearly show the structure of the device described in the utility model, some structures are omitted in the drawings to highlight the characteristic structures of the important parts. In the following, for the convenience of description, unless otherwise specified, slices refer to bio-based nylon 56 slices.

[0020] Example 1

[0021] This embodiment provides a nylon extraction system, which is arranged after the polymerization section 100 and before the drying section 200. Figure 1 As shown, the nylon extraction system includes a pre-extraction tank 310, a rotary valve 311, a mud pump 312, a first three-way reversing valve 313, a water-material separation tank 320, an extraction tower 330, a second three-way reversing valve 314, a centrifugal dryer 340, and a water circulation system 350. In addition, a bypass pipeline 315 is provided to connect the first three-way reversing valve 313 and the second three-way reversing valve 314.

[0022] The volume of the extraction tower 330 is 35m 3The extraction tower 330 is provided with a first water inlet 331, a second water inlet 332 and a third water inlet 333 in the middle of the tower body. The first water inlet 331 is provided in the middle of the tower body, and the second water inlet 332 and the third water inlet 333 are provided at the bottom of the tower body, wherein the second water inlet 332 is higher than the third water inlet 333. The extraction tower 330 is provided with a temperature measuring device not shown in the figure. There are 6 temperature measuring devices, which are evenly arranged in the height direction of the extraction tower 330. The temperature measuring device is connected to the PLC control system, and the PLC control system is connected to the water inlet regulating valve of each water inlet. The temperature measuring device can automatically detect the water temperature in the extraction tower and feed it back to the PLC control system, and then the PLC control system outputs a signal to the regulating valve of each water inlet to adjust the water inlet, thereby realizing the automatic control of the water temperature in the extraction tower 330. The tower body of the extraction tower 330 is provided with a heating area not shown in the figure. The heating area is a heating layer, which is used for heating and heat preservation of the entire extraction tower 330. An overflow port 334 is provided at the top of the extraction tower 330. The water discharged from the overflow port 334 can be directly discharged to the sewage treatment system, or can be treated to participate in the water circulation of the extraction device.

[0023] The centrifugal dryer 340 is provided with a slice outlet and a water outlet. The slice outlet conveys the dried slices to the drying section 200. The water outlet is connected to the water circulation system 350. The water circulation system has the function of regulating the temperature and filtering the water flow at the water outlet of the centrifugal dryer 340. The circulating water pipeline after water circulation treatment is divided into three routes. One route is adjusted to low-temperature water after heat exchange and is connected to the first water inlet 331 of the extraction tower 330. One route is connected to the second water inlet 332 after heating. And one route is connected to the third water inlet 333.

[0024] During the operation of the nylon extraction device of this embodiment, the bio-based nylon 56 slices pelletized by the pelletizing device of the polymerization section 100 are transported to the pre-extraction tank 310. In the pre-extraction tank 310, the slices and the hot water are in countercurrent. The slices move downward under the action of gravity, and the hot water flows from bottom to top, overflowing from the overflow port of the pre-extraction tank to the concentration system. In this process, the 90°C hot water (desalted water) and the bio-based nylon 56 slices undergo a heat transfer process, and the slice temperature rises. As the temperature rises, the small molecular substances remaining in the polymerization section precipitate outward and enter the hot water. Because the pre-extraction tank 310 is small in size and has a limited residence time, the pre-extraction tank 310 here mainly plays a preheating role, that is, preheating the slices from the polymerization section. If the slices directly enter the extraction tower, the slices heat up slowly, which may cause the slices to fail to meet the heating requirements, affecting the temperature of the slices in the extraction tower, and further affecting the extraction efficiency. Therefore, the slices are preliminarily heated and pre-extracted in the pre-extraction tank 310. The preheated slices are sucked into the mud pump 312 after passing through the rotary valve 311 disposed below the pre-extraction tank 310. In this embodiment, the rotary valve 311 plays a metering role and is used to control the output. Under the action of the mud pump 312, the slices and hot water are transported to the first three-way reversing valve 313.

[0025] When the extraction tower 330 works normally, the bypass line 315 is closed, and the slices and hot water enter the water-material separation tank 320 through the first three-way reversing valve 313, and the slices and hot water are separated in the water-material separation tank 320. After separation, the slices enter the extraction tower 330, which is filled with hot water at 90-95°C. The extraction tower 330 has a large volume, usually more than 15 times that of the pre-extraction tank, so that the slices can stay in the extraction tower 330 for more than 12 hours. During the 12 hours of slow flow from top to bottom, a large amount of small molecular weight monomers diffuse outward from the inside of the slices, and are eventually carried away by the water flow from bottom to top. The water flow carrying small molecular weight monomers overflows from the overflow port 334 of the extraction tower 330. The overflowing water flow can enter the concentration section for concentration, and the concentrated small molecular weight substances are then transported to the liquid phase polymerization section to participate in the polymerization reaction. The water temperature in the extraction tower 330 gradually decreases from bottom to top, so as to ensure that the small molecular weight substances in the bio-based nylon 56 slices are well precipitated to the surface during the flow from top to bottom, and then enter the hot water. That is to say, fresh hot water is continuously added to the extraction tower from the bottom of the extraction tower 330. The concentration of small molecular weight substances in the hot water at the bottom of the extraction tower is the lowest, and the concentration of small molecular weight substances in the hot water at the top is the highest. After the extraction is completed, the slices are transported to the centrifugal dryer 340 at a high place through a pipeline. Under the action of centrifugal force, the slices and water are separated. The moisture content of the slices after separation is controlled at about 7000-8000ppm, and then the slices are transported to the drying or solid phase thickening section. The water separated by the centrifugal dryer 340 enters the water circulation system 350 under the action of gravity. The water circulation system 350 is also connected to a desalted water pipeline 400 as a desalted water supplement for the entire extraction system. The circulation system 350 may include degassing equipment, heat exchange equipment, filtering equipment, circulating water pumps, etc., which are used for degassing, temperature adjustment, filtering and other processes of circulating water. Specifically, the water circulation system 350 mixes the water flow containing small molecular monomers separated by the centrifugal dryer 340 with fresh desalted water, and then divides the circulating water flow into three paths through temperature adjustment, degassing and filtering processes. One path directly enters the bottom of the extraction tower 330 and is connected to the third water inlet 333; one path enters the bottom of the extraction tower 330 after being heated by the heat exchange equipment and is connected to the second water inlet 332; and one path enters the middle of the extraction tower 330 after being cooled by the heat exchange equipment and is connected to the first water inlet 331. Among them, the temperature of the water introduced into the first water inlet 331 is about 20°C, the hot water introduced into the second water inlet 332 is about 98°C, and the temperature of the water introduced into the third water inlet 333 is about 80°C. The hot water introduced from the second water inlet 332 flows upward in the extraction tower 330, mainly playing the role of extraction; the water temperature introduced from the first water inlet 331 is relatively low, and is used to regulate the water temperature in the extraction tower 330 to prevent the temperature at the top of the extraction tower from being too high.The water flow introduced into the third water inlet 333 does not undergo heat exchange. The water flows downward at the bottom of the extraction tower 330, carrying the extracted slices to the centrifugal dryer 340, which plays a role in cooling the extracted slices and adjusting the liquid level in the extraction tower. The three water inlet volumes are automatically detected by the temperature measuring device on the extraction tower, and the water temperature in the extraction tower is fed back to the PLC control system. The PLC control system then outputs signals to the regulating valves set on the three water routes to adjust the water inlet volume, thereby realizing automatic control of the water temperature in the extraction tower 330. The water temperature adjustment speed is slow by only setting a heating layer on the outer layer of the extraction tower. In contrast, the use of three water inlets with different temperatures in this embodiment can more quickly and accurately adjust the water temperature in the extraction tower 330, avoid uneven outer wall temperature and internal temperature, and achieve better extraction effect.

[0026] When the extraction tower 330 fails and stops working, the pipeline from the first three-way reversing valve 313 to the water-material separation tank 320 is closed, and the pipeline from the extraction tower 330 to the second three-way reversing valve 314 is closed, and the bypass pipeline 315 between the two three-way reversing valves is opened at the same time, so that the slices processed by the pre-extraction tank 310 are directly sent to the centrifugal dryer 340, and then directly sent to the drying section 200, that is, the extraction tower 330 is skipped and the pre-extracted slices are directly dried, ensuring the continuous operation of the entire production line. Since the slices have been pre-extracted, the small molecular monomers in the slices have been partially removed, and directly entering the next section for a short time during the fault repair of the extraction tower 330 will not have a serious impact on the quality of the nylon slices. After the extraction tower 330 can work normally, the pipeline from the first three-way reversing valve 313 to the water-material separation tank 320 and the pipeline from the extraction tower 330 to the second three-way reversing valve 314 are opened, and the bypass pipeline 315 between the two three-way reversing valves is closed, and the nylon production line can continue to operate normally. The nylon extraction system of this embodiment can effectively prevent the production line from being shut down due to the failure of the extraction tower 330.

Claims

1. A nylon extraction system, characterized in that: The nylon extraction system comprises a pre-extraction tank, a water-material separation tank, an extraction tower, and a dehydration device which are arranged in sequence. The discharge pipeline of the pre-extraction tank is divided into at least two routes, one of which leads to the extraction tower, and the other route skips the extraction tower and directly leads to the dehydration device.

2. The nylon extraction system according to claim 1, characterized in that: The dehydration equipment is one or more of gravity dehydration equipment, screening dehydration equipment, centrifugal dehydration equipment, and filtration dehydration equipment.

3. The nylon extraction system according to claim 1, characterized in that: The nylon extraction system is arranged between the polymerization section and the drying section.

4. The nylon extraction system according to claim 1, characterized in that: The nylon extraction system is provided with a water circulation system, and the water circulation system circulates and transports the water separated by the dehydration equipment to the extraction tower.

5. The nylon extraction system according to claim 4, characterized in that: The circulating water pipeline passing through the water circulation system is divided into three routes, and the three pipelines are arranged from bottom to top at the interfaces on the extraction tower. The first route directly leads to the bottom of the extraction tower, the second route is provided with a heat exchanger and leads to the bottom of the extraction tower, and the third route is provided with a heat exchanger and leads to the middle of the extraction tower.

6. The nylon extraction system according to claim 1, characterized in that: The extraction tower is provided with an overflow port.

7. The nylon extraction system according to claim 1, characterized in that: A heating area is arranged on the tower body of the extraction tower.

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